Infusion systems for the delivery of liquid pharmaceuticals are widely used and relied upon by patients and care givers alike. Such delivery is generally made in one of two ways. The first is an immediate delivery from a health care provider or other operator in the form of a simple injection performed with a syringe and a needle directly disposed to the tissue of the patient. For this type of immediate delivery the amount of the pharmaceutical is typically measured by the health care provider or other operator and the rate of delivery is typically based on the speed at which they depress the plunger. Although overmedication can occur, the rate of delivery is rarely an issue with immediate delivery.
The second option is for gradual delivery, wherein a syringe or other reservoir is connected to specific medical tubing for delivery over time. With such time based delivery, overmedication and/or overdose of the pharmaceutical is a very real possibility. Syringes, or other pharmaceutical reservoirs such as fluid bags, are typically easily and commonly adapted for use with many different types of pharmaceutical, however the flow rate for proper delivery of such pharmaceuticals as determined by the manufacturer may very widely. Further, as patient needs and situations are often different, even when dealing with the same type of pharmaceutical it may be desired for different patients to receive flow rates, which again would be at or below the manufacturer's specified maximum delivery rate.
With the ever increasing desire to reduce health care costs, there is a market demand to reduce the costs of providing intravenous and subcutaneous administrations. With infusion over time, one option has been to employ programmable pumps that control the rate of flow, and while effective, such systems can be cost prohibitive for many users. In addition, many programmable pumps are based on the principle of constant flow. Because these systems attempt to maintain the same flow rate regardless of pressure, these systems generally incorporate a warning system to alert the user and/or operator of any dangerous increase in pressure as the pump attempts to maintain that constant flow. If there is an occlusion at the sight of administration, even with an alarm the patient may be injured and/or receive an overdose of the pharmaceutical.
In contrast to constant flow pumps, constant pressure pumps have been found to be safer and are often more financially acceptable to users. As they are generally more simple in construction, they may also lack some of the versatility of programmable flow rate pumps. One option to achieve a specific flow rate is to select tubing with an appropriate pre-set flow rate. Initially appearing to be a low cost option, providing a variety of different flow rate systems, each with a specific flow rate, leads to overhead complexity as well as potentially additional costs. With a large plurality of different systems greater storage and transportation costs and issue exist. Further, some systems may not be used as frequently as others, and confusion when identifying each distinct infusion system may occur. Further still, such specifically set infusion systems by their very nature do not permit the flow rate to change substantially over time, which if there is a desire to increase or decrease the flow rate over the course of administration, or over the course of use, make such single flow rate systems impractical.
Recently, there have been some advancements in flow regulators which strive to provide the user the ability to easily select and modulate the flow rate of a therapeutic agent or pharmaceutical liquid. In general, these flow regulators or flow constriction devices are designed to allow the user or operator to tune a dial and select a flow rate that corresponds to a level of flow constriction within the device.
U.S. Pat. No. 3,877,428 to Seagle, sets forth a Variable Infusion Control Device 10 for selectively controlling the rate of administration of fluids to a patient. The control device provides attachment fittings which allow it to be placed at any point along a supply tube between a reservoir and the patient. As set forth by Seagle, the variability of flow rate is accomplished with concentric capillaries 60 and 62 which may be variably inter connected, the overall length of the resulting combined capillary establishing the flow rate.
U.S. Pat. No. 5,234,413, to Wonder et al, strives to teach a simplified Infusion Rate Regulator Device with fewer elements—with only a gasket 68 disposed within the housing. Here again, Wonder varies the rate of flow not only as a function of the fluid metering groove 30 through which the fluid flows, but also as a function of the cross sectional area of the fluid metering groove 30. Interestingly, Wonder specifically cites to Seagle noting that the Seagle device is manufactured with five parts, raising manufacturing but more importantly resulting in an unacceptably high degree of variance in the tightness of fit between the parts which adversely impacts the consistency of flow rate at any setting.
U.S. Pat. No. 5,009,251 to Pike et al, teaches a flow regulator 22 having an extensive set of internal flow channels which operate as a capillary flow restrictor. Pike states that the length of the flow channel 114, the overall dimension of the control waver 46 and the slowest delivery rate are all interrelated, due to the known relationship of the flow rate through a capillary tube to the capillary tube's cross sectional area and length, which is mathematically described by Poiseuille's Law.
U.S. Pat. No. 6,095,491 to Kriesel, teaches an In-Line Flow Rate Control Device which again is stated as an option to costly and complex flow controllers. More specifically, Kriesel teaches a device 14 having a housing 20 made up of a base portion 22 and a cover portion 23. Disposed within a cavity are two hub portions 42, 46 which provide a fluid tight seal against a rotating knob 50, the rotating knob 50 providing a plurality of different flow restrictors which can be selectively moved into index place with flow passages in the base portion 22 and cover portion 23. These flow restrictors, i.e. orifices, may be microbors 70 of specific sizes, or frits 60 of different porosities.
US Patent Application 2003/0097097 to Scagliarini et al, teaches a Simplified Device for Regulating the Flow Rate of Medical Liquid Directed Towards A Patient. Once again, Scagliarini notes that many flow rate devices have five or more parts and do not actually achieve precise flow regulation. Scagliarini therefore teaches a device 1 having essentially three parts—a first portion 3 to be connected to a first conduit (not shown) of a medical infusion line connected to a reservoir of medical liquid, a second portion 4 to be connected to a second conduit of said line (also not shown) carrying the liquid to the patient, and a gasket 5 disposed between the first portion 3 and the second portion 4. Relative rotation between the first portion 3 and the second portion 4 permits different sized orifices 44, 52 and 66 provided respectively by the first portion 3, the gasket 5 and the second portion 4, to align with concentric recesses provided in second portion 4. By varying the length of flow through the concentric recess the rate of flow may be varied.
US Patent Application 2013/0138075 to Lambert also teaches a Variable Flow Control Device 200 that is provided by an inlet handle 110 providing an inlet port 116, an outlet handle 130 with an outlet port 134 and a seal 120 with orifices 116 enclosed/sandwiched between. Lambert specifically teaches a plurality of different sized orifices that may be selectively aligned between the inlet and the outlet to provide varied flow rate. In addition to specifically referencing Pike and Wonder for complexity, Lambert also discusses issues of alternative flow rate control by stating clearly, that “flow rate control in mechanical, elastomeric and other non-electrical pumps is generally accomplished with the use of certain small diameter tubing (rate set) that regulates the flow. This presents the following limitations: The flow cannot be adjusted during the infusion. Instead a new infusion set has to be used when a different rate is required. This adds cost and it may it may increase the risk of contamination. In order to change the flow rate, the tubing diameter has to change and thus multiple rate sets have to be made available and changed during infusion. This may or may not be possible during certain therapies. The nominal flow rate of these sets does not correspond to the flow rate during use due to the viscosity of the fluid often leading to patient and clinician confusion and errors.” Moreover, Lambert is clearly asserting the disclosed flow controller as an alternative to flow rate control based on tubing.
As varied as these and other prior art references are, in all cases an inherent problem may still exist. Each of the above devices appears to provide an option for no flow rate reduction—an open flow option. As such, although each device may permit some degree of flow control, there is a maximum flow rate that may well be dangerous to a patient.
Hence there is a need for a method and system that is capable of overcoming one or more of the above identified challenges.